Derusting 800 square feet of sheet metal quickly and moderately easily

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Hi there!

I have a lot of vertically mounted sheet metal that I need to derust.  It's about 800 square feet in total.  Annoyingly, it's on a site far away and I can't test anything ahead of time.

What's the fastest most economical way of doing this, off the top of your heads?

I've heard I could use a metal brush wheel on an angle grinder and I've heard I could use sand blasting.  I don't mind doing a little bit of manual labor, even if it's grueling, but I can only devote a few hours to this while on site (maybe 6 hours), so if it's *too* grueling I may not finish.

I've seen some YouTube videos where people will let things sit inside of a pan full of white vinegar overnight and that seems to work miracles, but this sheet metal is mounted vertically so I can't soak it in anything.   I've also seen YouTube videos where people use polycarbide abrasive wheels on their angle grinders and those seem to work faster than metal brush wheels, although the discs wear out faster.

What about a hybrid approach?  Spray the area with white vinegar first, let that sit for a few minutes, then hit it with the polycarbide wheel?

I estimate it's only about $5 for a few gallons of white vinegar and about $5 per abrasive disc from Harbor Freight.  Even if I blow through 10 discs that's only $50, or $55 altogether.

Sand blasting seems like it'd be significantly more expensive, plus require hauling out more kit.

[nereo]

First off - include a good respirator that can filter out small particles (~0.1µm) if you plan on sanding/grinding this much rust. 

If it were me I'd try vinegar in a pump-sprayer followed by a wire brush letting the vinegar soak for a couple hours.  However, if you use vinegar (or HCl -must faster acting but more safety concerns) you'll need to spray it off when you are done.  Whether you need to use a grinder depends on how much oxydation you have...
800sqft is a lot of surface to cover...

[lthenderson]

Whenever rehabbing rusty metal sided buildings, I simply knock off the loose flakes of rust either with wire brushes or with a wire brush attachment on a grinder for larger flat spaces, seal it with a good primer and then paint over that. As long as you get the loose rust, it isn't going to get any worse once you seal out the oxygen with the primer. The only reason I would go down to bare metal is because I want an absolutely smooth finish when I'm done, i.e. the body of a car. I've never seen anyone that particular on metal siding on a building.

If you go with the vinegar soaking route, you then have to wait for things to get absolutely dry before sealing it with primer or you will get blistering. This might be difficult to do if you only have six hours at a time and have to travel a long ways to get to the site.

[thedigitalone]

You just want the rust gone, and you aren't worried about the finish afterwards?  Look up Evapo-Rust rust remover at your local hardware store, it'll make the rust go away with minimal effort.

The drawback is the cost, $23 for about 20 sq feet, so that project would use $900+ in product.

[Fishindude]

You should be able to get most of it off with a pressure washer.

[WranglerBowman]

as lthenderson mentioned and I would recommend to use an angle grinder with a wire brush attachment to get all the loose rust off (not down to bare metal), then power wash real good, and use soap if there's any oily product on the metal, hit with a good primer (rust bonding) and then paint.  You should get really good results.

[M2 pilot]

I've heard of people getting good results with Barkeepers Friend.  Probably due to the oxalic acid content.  One could probably get oxalic acid cheaper. Previous poster mentioned EvapORust.  I've had good results with it & it can be re-used.

[TomTX]

First off - include a good respirator that can filter out small particles (~0.1µm) if you plan on sanding/grinding this much rust. 

Look for a P100 or N100 rated respirator to keep from breathing particles.